The series follows a bumbling and incompetent cyborg cop named Inspector Gadget, who is sent on cases and missions by his boss, Chief Quimby. These schemes are often caused by his arch-nemesis, the evil Dr. Claw, head of the malevolent criminal agency M.A.D. With the unknown help of his brainy niece Penny, and her dog Brain, Gadget always comes out on top, usually resulting in Claw vowing revenge.
- Inspector Gadget ― Voiced by Gary Owens in the original version of the pilot and by Don Adams in the re-dubbed version of the pilot and the rest of the series.
- Dr. Claw/Brain/M.A.D. Cat- Frank Welker.
- Penny Brown ― Mona Marshall in the pilot, Cree Summer in the rest of the first season and Holly Berger in the second season.
- Chief Quimby ― Dan Hennessey in the first season and Maurice LaMarche in the second season..
- Corporal Capeman ― Townsend Coleman.